The invention refers to a method for the production of a semiconductor device such as a light-emitting component, having at least one column-shaped or wall-shaped semiconductor element, and in particular refers to a method for the production of a semiconductor device where at least one semiconductor element has a lateral thickness in at least one cross-section direction of less than 1 μm, in particular less than 500 nm. The invention furthermore refers to a semiconductor device having at least one column-shaped or wall-shaped semiconductor element, in particular a semiconductor device with at least one nanowire and/or at least one nanowall which is arranged on a substrate. Applications for the invention exist in the production of optical, in particular light emitting, electrical, electromechanical and/or electro-thermal components.
The production of semiconductor elements (nanostructured semiconductor elements) on a substrate which have characteristic dimensions in the submicrometer range is common knowledge. “Top-down” methods such as the selective etching of planar semiconductors, or “bottom-up” methods such as the epitactic growth of nanostructured semiconductors are known for the structuring of a substrate and the production of the semiconductor elements.
For example column-shaped semiconductor elements (nanowires, nanocolumns) (see for example US 2011/0127490 A1 or US 2007/0257264 A1) or wall-shaped semiconductor elements (nanowalls, nanoplates, nanodiscs) are produced on a substrate with the specified methods. Typically, nanowire heterostructures are produced which include segments with various types of crystal along a main direction of the semiconductor elements, e.g. with different chemical composition or different doping, in order to provide the semiconductor element with specific optical, electrical, mechanical and/or thermal properties.
It is furthermore known that these properties of nanostructured semiconductors differ from semiconductors which are planar or have a bulk shape because the structuring influences the conduction properties and band characteristics. It is pointed out in US 2011/0127490 A1 that the nanowires are characterised by a negligible number of dislocations compared to planar semiconductors due to an effective stress relaxation.
The production of light emitting components (light emitting diodes, LEDs) from nanostructured semiconductors has been proposed. For example, K. Kishino et al. (“Proceedings of SPIE”, Volume 6473, 2007, P. 6473T-1-64730T-12) and A. Kikuchi et al. (in “Japanese Journal of Applied Physics”, Volume 43, 2004, P. L1524-L1526) describe LEDs which consist of (In,Ga)N/GaN nanowires on sapphire or silicon substrates and which emit light in the visible spectral range. The nanowires are formed as heterostructures by self-organisation, whereby sections of a crystal type with a lower band gap (quantum well sections) alternate with sections of a crystal type with a larger band gap (barrier sections) in the main direction of the nanowires. The wavelength of the emitted light is determined in particular by the band structure of the quantum well sections and specifically their content of In. B. Guo et al. (see “Nanoletters”, Volume 10, 2010, P. 3355) describe an LED made of (In,Ga)N/GaN nanowires on a silicon substrate, which emits various wavelengths in a broad spectral range (white light) by a variation of the semiconductor composition along the nanowires.
The production of LEDs with nanostructured semiconductors produces expectations of advantages compared to conventional GaN-based LEDs in terms of the growth conditions (possible use of silicon as substrate), the quantum yield of light emission and the adjustment of spectral properties (use of higher concentrations of In). However in practice until now only the few process parameters have been used to adjust specific emission properties which are also used in conventional LEDs, such as the composition of the semiconductor. In particular the adjustment of the emission of a specific spectral range, e.g. the adjustment of a white light emission, constitutes a great challenge for the control of procedural parameters in the production of the nanostructured semiconductors.
The specified problems not only have an effect on the production of LEDs, but also on other uses of nanostructured semiconductors, e.g. as electronic components, as electro-thermal components or as electromechanical components (MEMS components).